Fiber optic backlighting panels are commonly used to illuminate a high contrast image that is visible even under poor ambient light.
Typically, such prior backlighting devices utilize a plurality of optical fibers, each having a core surrounded by cladding, which are placed adjacent one another above an optically reflecting surface. Light is beamed into the optical fibers from a light source, such as a lamp. The light is propagated in the core of the optical fiber by means of partial internal refraction, and exits at one or more discontinuities in the fiber, providing local illumination in the region of the discontinuity.
In the past, such fiber optic backlighting devices have been manufactured from fiber optic substrates comprising one or more optical fibers grouped together in a rectangular ribbon or panel substrate configuration. Typically, the ribbon or panel substrate is about 0.01 to 0.03 thick. By deforming (for example, by a heated die) or machining (for example, by a computer-controlled laser beam) at least one surface of the substrate, local discontinuities are formed in at least some of the fibers at which some or all of the light introduced into one or both ends of the fiber will exit. Such illumination may be utilized for backlighting a variety of displays.
Analog indicators in automotive and other applications, such as speedometers, fuel level indicators, dial gauges, and the like, are traditionally arranged in the form of a circular annulus, or an angular segment of an annulus. In theory, such indicators can be backlit with one or more rectangular panels covering the entire area. However, backlighting the entire area of an annular indicator is inefficient and interferes with the use of the area in the middle or the corners of the display for other devices and mechanisms, such as a self-contained digital readout.
For such applications, it is thus desirable to use fiber optic illumination ribbons and panels having a curved shape. To date such curved shapes have been laid up one strand at a time, using a flat template defining the desired shape. Thus a need exists for a method and apparatus for the mass production of arrays of optical fibers that is not limited to rectangular panels and ribbons.